1. Field of the Invention
The present invention relates to a heat treatment apparatus for and method of heat-treating a semiconductor substrate, a glass substrate for a liquid crystal display, a glass substrate for a photomask, a substrate for an optical disk and the like (referred to hereinafter as xe2x80x9csubstratesxe2x80x9d) which are coated with a processing solution of a low-dielectric-constant material and the like to form a predetermined film such as an interlayer insulation film on the substrates, and a substrate processing apparatus having the heat treatment apparatus incorporated therein.
2. Description of the Background Art
Conventionally, circuit patterns formed on the substrates have multi-layer interconnections, and it is important that an interlayer insulation film between the multilayer interconnections has a flatness and an insulating property (or a low dielectric constant). Such an interlayer insulation film is formed by coating a substrate with a low-dielectric-constant material such as SOD (Spin-on-Dielectronics) or polyimides and then firing the substrate by heat treatment.
An interlayer insulation film has been conventionally formed from a polyimide coating, for example, by a method to be described below. First, a spinning-type coating apparatus (a spin coater) or the like is used to uniformly coat a substrate with a processing solution of a polyimide. The substrate coated with the polyimide processing solution is transported into a chamber of a heat treatment apparatus for heat treatment. The substrate is then placed on a hot plate heated to a predetermined temperature within the chamber. After the transportation of the substrate into the chamber, a nitrogen gas is introduced into the chamber to provide a low oxygen concentration atmosphere within the chamber. When the substrate is heated to not less than the critical temperature for reaction (referred to hereinafter as a xe2x80x9ccritical reaction temperaturexe2x80x9d) of the polyimide in the low oxygen concentration atmosphere, a chemical reaction occurs in the polyimide on the substrate to form an interlayer insulation film having a relatively low dielectric constant and a high degree of flatness.
However, the formation of the interlayer insulation film by the above-mentioned background art method presents problems to be described below.
To reduce the dielectric constant of the interlayer insulation film, it is necessary to heat the substrate coated with the processing solution of polyimides, SOD or the like in a low oxygen concentration atmosphere. In the background art method, the substrate is heated up to a predetermined temperature immediately after the substrate is transported into the chamber in which the ambient atmosphere is left. This increases the dielectric constant of the interlayer insulation film.
More specifically, as the substrate coated with the processing solution of polyimides, SOD or the like is transported into the chamber, outside air flows into the chamber to cause the oxygen concentration in the chamber to approach the oxygen concentration in the ambient atmosphere. For this reason, the nitrogen gas is introduced into the chamber to provide the low oxygen concentration atmosphere within the chamber. However, during the time between the instant immediately after the transportation of the substrate into the chamber and the instant at which the low oxygen concentration atmosphere is provided, the substrate is heated to not less than the critical reaction temperature at which a chemical reaction occurs in the processing solution coating the substrate. As a result, the chemical reaction occurs in an atmosphere of a relatively high oxygen concentration to cause oxygen molecules to be introduced into the interlayer insulation film, thereby forming the interlayer insulation film having a relatively high dielectric constant.
To prevent the above phenomenon, the heating of the substrate up to not less than the critical reaction temperature is required to await a predetermined oxygen concentration or lower reached within the chamber into which the nitrogen gas is introduced after the transportation of the substrate into the chamber. However, it takes much time for the oxygen concentration within the chamber to reach the predetermined oxygen concentration or lower. This presents another problem in low processing efficiency.
Additionally, if the substrate heated to an elevated temperature is transported out of the chamber immediately after the completion of the heating process, oxygen molecules are introduced into the interlayer insulation film, thereby increasing the dielectric constant of the interlayer insulation film formed by the firing process. It is therefore necessary to transport the substrate out of the chamber after the substrate is cooled down to a temperature lower than the critical reaction temperature in the low oxygen concentration atmosphere within the chamber. However, it also takes much time to cool down the high-temperature substrate within the chamber, and the problem of low processing efficiency as in the heating process is also encountered.
The present invention is intended for a heat treatment apparatus for performing heat treatment upon a substrate coated with a processing solution to form a predetermined film on the substrate.
According to the present invention, the heat treatment apparatus comprises: a processing chamber having a low oxygen concentration atmosphere maintained therein for performing the heat treatment upon a substrate; a heater in the processing chamber for placing thereon the substrate loaded into the processing chamber to heat the substrate; a loading/unloading unit movable into and out of the processing chamber for loading and unloading the substrate into and out of the processing chamber; and a cooling part in the loading/unloading unit for cooling the substrate held by the loading/unloading unit.
The heat treatment of the substrate is performed in the low oxygen concentration atmosphere to form the predetermined film having a low dielectric constant. Additionally, rapid heating and cooling provide high processing efficiency.
Preferably, according to one aspect of the present invention, the processing chamber comprises an opening through which the substrate is loaded into and unloaded out of the processing chamber by the loading/unloading unit, and the heat treatment apparatus further comprises: an opening/closing part for closing or opening the opening; and a nitrogen gas supply part for supplying nitrogen gas into the processing chamber, wherein the nitrogen gas supply part supplies the nitrogen gas into the processing chamber at least when the opening/closing part opens the opening.
This prevents outside air from entering the processing chamber through the opening to avoid the entry of oxygen into the processing chamber, thereby ensuring the above-mentioned effects.
Preferably, according to another aspect of the present invention, after receiving the substrate heated by the heater, the loading/unloading unit places the substrate in a standby condition within the processing chamber until the temperature of the substrate becomes lower than a predetermined temperature, and then exits from the processing chamber.
The substrate is held in the low oxygen concentration atmosphere until the temperature of the substrate becomes below the predetermined temperature. This ensures the above-mentioned effects.
The present invention is also intended for a substrate processing apparatus for coating a substrate with a processing solution and performing heat treatment upon the substrate to form a predetermined film on the substrate.
The present invention is also intended for a method of performing heat treatment upon a substrate coated with a processing solution to form a predetermined film on the substrate.
It is therefore an object of the present invention to provide an apparatus for and method of heat treatment which is capable of forming a predetermined film having a low dielectric constant and which is high in processing efficiency, and to provide a substrate processing apparatus having the heat treatment apparatus incorporated therein.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.